The present invention concerns a multi-layer planar inductance coil as set forth in the classifying portion of claim 1 and a process for producing such a multi-layer planar inductance coil.
Planar inductors of that kind are used for example in switching power supplies, voltage transformers or other items of equipment in power electronics, which are designed on the basis of a multi-layer support plate (so-called xe2x80x9cmulti-layerxe2x80x9d or xe2x80x9cmulti-layer print platexe2x80x9d) which has a plurality of conductor layers which are electrically insulated from each other. More precisely, such a multi-layer support plate, besides electronic components for the switching electronics which are suitably connected by one or more conductor tracks of the multi-layer plate, has inductance coils such as transformers or chokes for which conducting layers (in mutually superposed relationship) of the multi-layer plate perform the functions of the windingsxe2x80x94that is to say for example the primary or secondary winding of a transformerxe2x80x94: for that purpose a transformer core is fitted suitably through an opening in the multi-layer plate and then forms the desired transformer, together with the windings formed on the conducting layers of the multi-layer plate.
It is then possible in that way to produce an item of equipment which is of a compact structure and which is stable in regard to thermal and mechanical properties and which is markedly superior to other conventional design configurationsxe2x80x94for example a discrete transformer on a conventional print platexe2x80x94and is particularly suitable for commercial use.
FIG. 6 relating to the state of the art shows in the sectional side view therein the structure of such a planar inductance coil constituting the general kind of device involved.
Mounted on a portion, forming a planar inductor, of a multi-layer plate 70 which has a plurality of electrically conducting layers 72 is a diagrammatically shown transformer core 74 whichxe2x80x94approximately E-shaped in side sectionxe2x80x94extends with limbs (not shown in the Figure) through openings of suitable size in the multi-layer plate 70. In that respect, to co-operate with the transformer core 74 the conducting layers constitute a corresponding primary or a secondary winding so that in the illustrated manner the inductor is directly embedded into the peripheral electronics diagrammatically indicated with the further electronic components 76, or is connected thereto by way of corresponding conducting layers 72.
The structure shown in FIG. 6 thus provides an extremely compact, electrically and mechanically stable arrangement which in addition is also extremely suitable for mass production by virtue of the good reproducibility of the geometrical dimensions involved.
Depending on the respective purpose of use and the specifically designed electronic unit, it is possible in that way to implement one or more planar inductance coils on or in a multi-layer plate, although in this case the inductance coils usually occupy only a fairly small part of the multi-layer plate surface or mounting surface.
It has been found however that there is the disadvantage in terms of using that technology in the context of a product program with a relatively large number of alternative structural configurations that a special design for the associated multi-layer plate must be implemented for each individual or separately produced alternative configuration; thus, particularly in the case of power supply circuits, it is necessary to afford both the primary side and also the secondary side of the (planar) transformer for a plurality of different voltages or voltage ranges, for example also dimensioned by the selected number of relevant conducting layers for the transformer (corresponding to a number of windings of the transformer). With for example five possible different primary voltages and five appropriate different secondary voltages, accordingly there would be 25 alternative product configurations of an electronic device, which each require a separate multi-layer plate which is specifically designed for the respectively desired voltage combination, with diversification occurring only in the region of the respective planar inductance coil or coils.
If it is then borne in mind that in particular multi-layer plates with a relatively high number of layers (for example eight or eleven layers), compared to multi-layer plates with a low number of layers, give rise to over-proportionally high purchase costs and accordingly storage costs, in particular the desired flexible use of the multi-layer technology is extremely expensive and is not competitive with conventional technology when an increasing multiplicity of alternative design configurations is involved.
Therefore the object of the present invention is to provide an arrangement of the general kind set forth, having a multi-layer planar inductance coil, the manufacture of which can be simplified and made flexible in regard to possible variations in the inductance coil windings, while in particular also the provision and stocking of the expensive plate-shaped supports which are in the form of multi-layer plates can be simplified.
That object is attained by the multi-layer planar inductance coil having the features of claim 1 and the method having the features of claim 9.
Advantageously in that respect the second multi-layer member which is provided in said portion and which is preferably also limited with its dimensions to that portion permits the flexible, variable addition of additional conducting layers and thus inductor windings to the first conducting layers which are already present in the base multi-layer member (the first plate-shaped support) so that by suitably applying and configuring one or more locally limited multi-layer members it is possible to produce the inductance coil required for a respective alternative product configuration, at low cost, without the need for example to provide a special, separate multi-layer complete design for that alternative product configuration.
As moreover a relatively large number of electrical conducting layers is generally required only in the region of the planar inductance coil, but not for the surrounding peripheral electronics, it is in accordance with the invention and advantageously possible for the peripheral electronics to be implemented on the first support with a small number of conducting layers (at a corresponding low level of cost), while it is only in the region of planar inductance coil that the required additional conducting layers are locally and selectively afforded by the provision of one or more additional multi-layer members.
Accordingly the expensive multi-layer material is then put to optimum use.
In addition is advantageously possible by means of the present invention to develop a manufacturing system which is suitable for a large number of alternative configurations and which includes components that embrace the alternative configurations, on the first, plate-shaped support, while components which are specific to alternative configurationsxe2x80x94besides additional windings, possibly also additional, specifically necessary peripheral electronicsxe2x80x94are contained on the additional support or supports. The structural expenditure and stock-keeping for a large number of alternative design configurations are therefore drastically reduced.
Advantageous developments of the invention are set forth in the appendant claims.
Thus, it is possible in accordance with the invention to provide on one or both sides of the base support (the first support) one or more of the additional multi-layer supports which are limited to the specific region of the inductance coil, while in particular when mounting at both sides is involved, that can afford an arrangement involving maximum compactness.
The invention is also particularly suitable in regard to use of the planar inductance coil as a transformer as here the primary winding and the secondary winding can be directly associated with the conducting layers of the first and the second supports respectively and it is thus possible to directly influence the turns ratio depending on the respective specification concerned.
In accordance with the invention there are various possible ways of suitably connecting the second support mechanically (and also electrically) to the basic first support, in which respect a soldered connection in the lateral region of the second support has proven to be particularly suitable and preferred in terms of strength and mechanical load-bearing capability. Such an arrangement could further advantageously be supplemented or further stabilised by a (possibly additional) adhesive connection of the conductor layers.
All in all the present invention affords a planar inductance coil system which can be put to flexible use and which on the basis of the advantageous multi-layer technology affords the option of substantial production and logistical optimization.